An electrochemical sensor system will be developed that will measure carbon monoxide in the 0-10 part-per-million range in the presence of 0-200 ppm of hydrogen gas. This system will be useful for the prediction of neonatal jaundice, since carbon monoxide is generated during heme degradation and exhaled. However. electrochemical measurements are often confounded by exhaled hydrogen form intestinal microflora. The sensor "system" may consist of a selective permeation device that precedes a standard sensor, or a selective absorption device (such as a simplified gas chromatograph). The applicants will investigate the potential of developing a new type of sensor that is inherently insensitive to hydrogen.